In this single-centre, retrospective study, the medical records of patients diagnosed with intermediate or advanced CC who underwent laparoscopic radical surgery at the Affiliated Hospital of Jiujiang University (Jiujiang, China) between August 2018 and April 2021 were screened. In total, 80 patients who met the inclusion and exclusion criteria were included. The overall cohort had a mean age of 65.0 years (range, 48.1–74.3 years), with a male-to-female ratio of 48:32 (60.0% male). Given that this study is a retrospective analysis, the sample size was determined by the total number of eligible patients during the study period, and no a priori sample size or power calculation was performed. Patients were not prospectively assigned to treatment; instead, two historical cohorts were formed based on the standard perioperative practice at their respective times of surgery. Patients who underwent surgery during the earlier phase (August 2018 to March 2020) received the then-standard peritoneal lavage with saline and formed the control group (CG; n=38). Additionally, patients who underwent surgery during the later phase (April 2020 to April 2021) received intraoperative raltitrexed peritoneal infusion in addition to lavage and formed the observation group (OG; n=42).

The inclusion criteria were as follows: i) Pathological diagnosis of intermediate and advanced CC; ii) surgical resection performed by imaging evaluation before surgery; iii) complete clinical data; and iv) no abnormalities in routine blood, liver and kidney function indices within 1 week before treatment.

The exclusion criteria were as follows: i) Patients with other malignancies and other diseases that affect the study; ii) patients with abnormalities in routine blood, liver and kidney function indices within 1 week before treatment; iv) patients who had allergies for drugs used in this study; and v) pregnant women.

All patients underwent laparoscopic radical surgery for CC under tracheal intubation anaesthesia performed by doctors in the Three Branches of General Surgery. Raltitrexed (SFDA approval no. H20090325; 2 mg/pc; Nanjing Zhengda Tianqing Pharmaceutical Co., Ltd.) was selected as the intraperitoneal chemotherapy drug, and the dosage was calculated as 3 mg/m² according to the body surface area of the patient. The laparoscopic surgery procedure was as follows: i) After laparoscopic exploration to identify tumour-free tissue and determine the tumour location, normal tissue adjacent to the tumour was retracted with separating forceps to expose the diseased tissue. ii) During the operation, pulling and squeezing the tumour tissue was avoided. iii) The blood vessels were dissociated and ligated, with the vein addressed first, followed by the artery. iv) The patients underwent radical resection of the lesion, gastrointestinal reconstruction, trauma haemostasis and saline irrigation.

For the OG, before the abdomen was closed, raltitrexed was dissolved in 10 ml normal saline, diluted in 250 ml normal saline and poured into the abdominal cavity, with a focus on cleaning and irrigating the tumour site to ensure optimal effect of the drug in the abdominal cavity. The abdomen was closed, and the drainage tube was placed in the abdominal cavity and clipped for 2 h before opening.

For the CG, before the abdomen was closed, normal saline was poured directly into the abdominal cavity for repeated flushing and suction of the fluid. Abdominal closure and drainage were the same as those of the OG.

For haematological analysis, blood samples were processed immediately using a Mindray automated haematology analyser (Shenzhen Mindray Bio-Medical Electronics Co., Ltd.) according to the manufacturer's instructions, with the following reagents: Diluent (cat. no. 10300031), lysing agent (cat. no. 10300032) and cleaner (cat. no. 10300033) (all Shenzhen Mindray Bio-Medical Electronics Co., Ltd.). This system employs impedance counting and flow cytometry technologies to measure the number of white blood cells (WBCs), neutrophils (NEs), red blood cells (RBCs) and platelets (PLTs).

For tumour marker detection, blood samples were centrifuged at 3,000 × g for 10 min at 4°C to obtain serum, which was stored at −80°C until analysis. Carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) levels were measured using Elecsys^® CEA and CA19-9 electrochemiluminescence immunoassay kits (cat. nos. 05200067 190 and 11731676 122, respectively; Roche Diagnostics GmbH) on Roche E601 and E602 electrochemiluminescence analysers according to the manufacturer's instructions.

As the main outcome measures, the therapeutic effects were compared between the OG and the CG. Changes in routine blood indicators (WBCs, NEs, RBCs and PLTs) and tumour markers (CEA and CA19-9) were observed.

As the secondary outcome measures, the basic clinical data of the patients were compared. Adverse reactions that occurred during treatment, such as nausea and vomiting, abdominal distension, diarrhoea and incisional infections, were also recorded and the reaction rates were calculated using the following formula: Total adverse reaction rate=(number of total adverse reactions/total number) ×100.

A complete response (CR) was indicated by the total disappearance of the target lesions, no appearance of new lesions and the maintenance of normal tumour markers for at least 4 weeks. A partial response (PR) was indicated by a ≥30% reduction in the sum of the maximum diameter of the target lesion, which was maintained for at least 4 weeks. Progressive disease (PD) was indicated by a ≥20% increase in the total diameter of the target lesion relative to the total minimum diameter of the pretreatment lesion, an absolute increase in the total diameter ≥5 mm or the appearance of a new lesion. Stable disease was indicated by a decrease in the sum of the maximum diameter of the target lesion without reaching a PR or an increase without reaching PD. Remission rate=(CR + PR)/total number of cases ×100.

The collected data were analysed with SPSS Statistics (version 20.0; IBM Corp.) and visualised with GraphPad Prism (version 8.0; GraphPad; Dotmatics). The normality of the continuous data distribution was confirmed using the Kolmogorov-Smirnov test (all P>0.05). Continuous data are presented as the mean ± standard deviation. Baseline characteristics between the two groups were compared using independent samples t-tests for continuous variables and χ² or Fisher's exact tests for categorical variables. For the primary outcomes (haematological indices and tumour markers), which involved comparisons across treatment groups and time points, two-way analysis of variance (ANOVA) was employed to assess the effects of treatment groups, time and their interaction. The Šídák multiple comparisons test was used for post hoc analyses to control for the familywise error rate associated with multiple comparisons. Categorical data (for example, remission rate and adverse reaction rate) are presented as n (%) and were compared using a χ² or Fisher's exact tests as appropriate. A two-tailed P-value of <0.05 was considered to indicate a statistically significant difference.

With respect to the basic clinical data of the two groups, there was no significant difference with regard to age, sex, tumour site, clinical stage or differentiation degree (P>0.05), as shown in Table I.

The treatment effects for both groups were analysed and compared. The disease remission rate in the CG was significantly lower than that in the OG (P=0.014), as shown in Table II.

Two-way ANOVA revealed that while all haematological indices significantly changed over time (all P<0.0001 for time effects), no significant differences between the OG and CG were observed at either the preoperative or postoperative time points for WBC, NE, RBC or PLT (all group effects and interactions, P>0.05) (Table III). Post hoc Šídák tests confirmed that WBC and NE counts increased significantly (both P<0.0001), whereas RBC and PLT counts decreased significantly (both P<0.0001) from preoperative to postoperative measurements in both groups (Fig. 1).

Analysis of tumour markers using two-way ANOVA revealed significant main effects of time for both CEA and CA19-9 (both P<0.0001), with levels decreasing postoperatively in both groups (Table III). Notably, significant group effects were observed for both markers (CEA: P=0.038; CA19-9: P=0.029), and Šídák's post hoc tests confirmed that the observation group had significantly lower levels than the control group at the postoperative assessment (CEA: adjusted P=0.021; CA19-9: adjusted P=0.013). No significant differences were found between the groups preoperatively (both adjusted P>0.05) (Fig. 2).

No significant differences were found with regard to the total incidence of postoperative adverse reactions between the two groups (P>0.05), as shown in Table IV.